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arp cache time

FranzR
New Contributor
Dear Community,

when does a arp entry in the cache of a vsp-Switch deleted?
Can this be modified?

Our problem is that we use a 60 minutes lease time at the DHCP server. And sometimes the NAC System reports a ARP spoofing event if DHCP server offers a new client a IP adress because of lease time. But in the arp cache of the Switch this IP belongs to the older MAC adress.

Thanks

Franz
1 ACCEPTED SOLUTION

WillyHe
New Contributor III
Hello Franz,

The default arp time-out for VSP and ERS switches is 6 hours, you can see that when executing "show ip arp", at the end of the table following information is provided.
====================================================================================================
IP Arp Extn - GlobalRouter
====================================================================================================
MULTICAST-MAC-FLOODING    AGING(Minutes)    ARP-THRESHOLD
----------------------------------------------------------------------------------------------------
disable                                           360                          500
c: customer vid u: untagged-traffic
30 out of 35 ARP entries displayed
ARPs on TX-NNI: Current = 0, re-ARP count = 4

If you like it is possible to change the ARP time-out
SA-02:1(config)#ip arp timeout ?
<1-32767> Arp lifetime in minutes

When using VRF's you must change ARP time-out for each VRF.

hope this helps

regards
WillyHe

View solution in original post

1 REPLY 1

WillyHe
New Contributor III
Hello Franz,

The default arp time-out for VSP and ERS switches is 6 hours, you can see that when executing "show ip arp", at the end of the table following information is provided.
====================================================================================================
IP Arp Extn - GlobalRouter
====================================================================================================
MULTICAST-MAC-FLOODING    AGING(Minutes)    ARP-THRESHOLD
----------------------------------------------------------------------------------------------------
disable                                           360                          500
c: customer vid u: untagged-traffic
30 out of 35 ARP entries displayed
ARPs on TX-NNI: Current = 0, re-ARP count = 4

If you like it is possible to change the ARP time-out
SA-02:1(config)#ip arp timeout ?
<1-32767> Arp lifetime in minutes

When using VRF's you must change ARP time-out for each VRF.

hope this helps

regards
WillyHe